Senator Seselja was promoted to the frontbench in Prime Minister Malcolm Turnbull's cabinet reshuffle on Monday, a widely-tipped move that has made him the first Canberra Liberal in history to reach the ministry.

The senator was one of three to become assistant ministers, and he will now work closely with Christian Porter, who remains minister for social services.

The appointment comes as the federal government prepares to glean billions of dollars of savings from welfare spending, a pledge that was made just days out from the election to help fund other campaign promises.

Senator Seselja told Fairfax Media on Monday the welfare reforms were "critically important", and that payments needed to be better targeted to those who needed them.

He identified welfare dependency as a significant issue, and as a major drain on the federal budget.

"The goal is to make sure that those who need the help, get the help, and get proper help," he said.

"We do want to have a culture in this country that, to the maximum extent possible, encourages those who can work, to work."

The exact breakdown of Senator Seselja's responsibilities within the portfolio were not clear on Monday afternoon, and it is unknown whether he will have any direct responsibility for implementing the government's election pledge to make $2.3 billion in welfare savings.

He has chaired the Parliament's community affairs committee for the past two-and-a-half years, a role he says has given him considerable experience in the social services portfolio.

The promotion came despite Senator Seselja, a conservative, being a strong and public backer of former prime minister Tony Abbott during last year's leadership challenge.

Asked whether he had thought his support for Mr Abbott had hurt his prospects for promotion, Senator Seselja said: "I'm a big believer that you make the call that you believe in and you don't try and think too much about personal advancement.

"I made my views known at the time … but I'm not focused on the past, I'm focused on this term of government."

The promotion drew praise from his colleagues in the ACT Legislative Assembly, with Canberra Liberals leader Jeremy Hanson saying it was "great news for Canberrans" that a local senator would be represented in the federal ministry.

"Having been leader of the Canberra Liberals for two local elections before entering the Senate, Zed is well acquainted with Canberra's needs and he'll be well placed to lobby for the ACT as part of the federal ministry," Mr Hanson said.

Senator Seselja said it was a "great privilege" and that the appointment of an ACT Liberal senator to the ministry was "long overdue".

ACT Labor Senator Katy Gallagher criticised the appointment of a senator who supported the watering down of the Racial Discrimination Act to the portfolio of multicultural affairs.

Last year, Senator Seselja said he would have supported changes to section 18C of the Act, which makes it illegal to say anything that would insult or offend someone on the basis of their race or ethnicity.

Senator Gallagher said her opponent's views were out of touch with the community.

"It is extremely alarming that one of the few people who wants to water down these protections against racist hate speech has been appointed to this portfolio," she said.

Prior to the reshuffle, there was speculation that conservatives would be promoted to ease tensions within the Coalition.

Senator Seselja said he believed he had been promoted on merit.

"In the end, the reason for the appointment is a matter for the Prime Minister," he said.

"I understood it to be based on merit, first and foremost. That's the way I see it, and that's the way I'll be approaching it."